Perhaps we are all getting gym-weary, tired of the complexities of Body Pump and Gyrotonics, because it seems that that most basic and natural of activities - walking - is enjoying a resurgence in popularity among those on a quest to get fit. Personal trainers can be spotted power-walking people around London's parks, fitness gurus are churning out books on the subject and even the medical profession gives its renewed backing to a daily walk. This month sees the launch of the National Step-O-Meter programme, a joint initiative by the British Heart Foundation and the Countryside Agency to get us all out walking. Through their GP, practice nurse or health visitor, all NHS patients who sign up to the scheme can borrow a pedometer free of charge.

There is little doubt that, for the previously sedentary, walking is a good idea. In her new book, The GI Walking Diet, the fitness expert Joanna Hall lists the health benefits of walking as everything from reducing the risk of gallstones and strokes to alleviating sleep problems and, of course, helping you to lose weight. Indeed, in recent months, leisurely walking (at 2 miles per hour) was found by researchers at the University of Colorado to be the best formula to help obese people shed pounds and, in a study published in the Annals of Internal Medicine, to prevent peripheral artery disease (which impairs blood flow in the legs and causes leg pain in one-fifth of elderly people). Last week, experts even suggested that walking ability was the most accurate predictor of illness and death in elderly people.

But beyond its body maintenance and disease-fighting effects, will clocking up the requisite daily steps take you to the next step, enabling you to lose weight and get super-fit? Or is it just a bit of a cop-out? Not if you do it properly, according to Hall: "Although taking 10,000 steps a day will improve your health, it may not have a significant effect on your weight loss or fitness unless it is performed in the right way." By that she means incorporating 10-minute bursts of fast walking into your daily plan. To lose weight requires even more effort - you would probably need to tot up at least 16,000 steps a day of walking before the pounds start dropping off, Hall says.

Adding hills or challenging terrain will speed up calorie burning. Walking on softer surfaces, such as mud, sand or grass, automatically means you use more energy than you would walking on concrete or Tarmac; every time your foot hits the ground it creates a small depression so that the leg muscles must work harder to push upwards and forwards for the next step. Walking on cobblestones, or on as rocky ground as you can find, may have even more profound benefits. Last year, physiologists at the Oregon Research Institute found cobblestone-walking, an activity rooted in traditional Chinese medicine, leads to significant reductions in blood pressure and improvements in balance. It is thought that the uneven surfaces may stimulate acupressure points on the soles of the feet, thereby regulating blood pressure. Because it is challenging, it will also burn more calories.

For even faster weight loss results, though, you could always try Nordic walking (or urban trekking as it is known in the US), an activity that despite looking naff (the idea is to hike through the urban jungle with two ski poles), does have proven benefits. Professor John Pocari, an exercise physiologist at the University of Wisconsin, says using walking poles forces people to pick up their pace and work harder without realising it.

"Just the fact that you are using your arms through a greater range of motion than normal means you are increasing calorie expenditure," Pocari says. On average, a person who walks three miles in a workout will burn 100 calories per mile - add poles and they can burn an additional 20%, says Pocari. Participants in his studies were also found to increase their upper-body strength by 40% and, compared with running, he estimates walking with the poles or without reduces impact on vulnerable hips, ankles and knees by 26%.

There is growing evidence that by striding out more often you will improve your mental health too. At the University of Illinois, researchers compared the effects of a walking programme with a toning and stretching regimen in elderly subjects and found that walkers performed far better in tests of mental agility. Professor Arthur Kraemer, who led the study, said walking, like other forms of aerobic exercise, increases oxygen supplies and blood flow to the brain, helping it to stay more alert and work more efficiently. Even if a 20-minute power walk at lunchtime is all you manage, it could be comparable to a course of psychotherapy after six weeks, found psychologists at the University of Illinois.

Some even claim that walking is on a parallel with yoga in its ability to unite body and mind. Rebecca Gorrell, director of movement therapy at Canyon Ranch spa, the celebrity bolthole in Arizona, believes taking a power-walk is akin to meditation. She encourages those weary of publicity and life to walk away their worries on regular hikes in the surrounding countryside. "The idea is that you empty your mind of thoughts, to concentrate on the present, not what happened yesterday or what might happen tomorrow, when you walk," says Gorrell. "Don't think about how hard you are working, but shift your thoughts to your breathing. Inhale deeply through your nose and exhale through your mouth."

While it may reunite you with your inner self, the real beauty of walking is its simplicity and convenience. "Nobody is intimidated by the idea of it," says Lorna Malcolm, the Reebok master trainer. "Once you have got somebody out walking, you can start to push them to a new level by getting them to walk faster or further." And it is a habit that sticks. A survey by the Countryside Agency as part of its Walking for Health initiative found that half of those given a pedometer still used them two years later and 93% of subjects were walking greater distances as a result.